Recoilless gun



C. N. HICKMAN RECOILLESS GUN May 27, 1952 2 SHEETS-SHEET 2 Filed April 21, 1945 Patented May 27, 1952 REcoILLEss GUN Clarence N. Hickman, Jackson Heights, N. Y., assignor to the United States of America as represented by the Secretary of War Application Aprilr21, 1945K, Seri-al No. 589,500

2 claims.

'I'he `invention described hereinmay be manu! factured and used by or for the .Government for governmental purposes Without the payment to me of any royalty thereon.

This invention relates, generally, t a recoilless gun, and more particularly to a recoilless attachment adapted to convert the conventional 4.2 inch chemical mortar into a lightweight, readily portable, weapon.

Ordnance such as the conventional 4.2 inch chemical lWarfare service mortar (described on pages 371-379, Chemicals in War, Prentiss, Mc- Graw-Hill Book Co., 1937) is necessarily heavy because of the recoil forces which must be absorbed. Such guns usually require a sturdy mount and/or a heavy base plate which are not easily moved and set up under battle conditions. The` conventional base plate for the 4.2 inch chemical mortar weighs about 185 pounds.

As av result of my research and experiments inthe development of rockets and propellants for rockets, I have determined that ordnance such as the chemical mortar may be converted into a relatively light weight weapon by replacing the conventional mortar tube cap with a reaction chamber having an open nozzle or venturi. The use of such a chamber provides a recoilless gun which may be supported on a light weight mount and which requires no base plate.y

Such a recoilless gun may be easily broken down for transportation into three components each weighing less than 50 pounds.

It is therefore one of the objects of this invention to provide a light Weight gun of the recoilless type which is readily portable. v

, It is another object of this invention to provid a muzzle loaded recoilless gun.

It is a further object of this invention to provide a recoilless attachment adapted to be utilized with the conventional barrel or tube of the 4.2 inch chemical warfare service mortar.

It is a further object of this inventionV to provide a recoilless attachment for the chemical mortar Which sets up rforces counteracting the tendency of the mortar to rotate during firing.

Stillanother important object ofthe invention is the provision. of a recoilless attachment for muzzle loading mortars with means forvadjusting the attachment to compensate for manufacturing tolerances and erosion.

Other objects and advantages of the `invention will be readily apparent from the following description Vof the accompanying drawings in which:

Fig. 1` is anelevational View partly in section of a preferred construction of'a recoilless combustion lchamber secured to theend of a mortar tube;

of the combustion chamber shown in Fig. 1, showing one of thefplurality of vanes provided in the combustion chamber, nozzle;

Fig. 2 is an end elevation viewof a portion Fig. 3 is a vertical sectional view of a modified construction of combustion chamber secured tothe end of a mortar tube; ,Y

Fig. 6 is a Vertical sectional view of a recoilless combustion chamber having` an adjustable throat; and

Fig.7 is a vertical sectional vieW of a modified recoilless combustion chamber having an adjust-` able throat.

Referring tothe drawings for the purposes of illustration, in the embodiment of my invention shown in Fig. 1, the rear end of a conventional 4.2 inch chemical warfare service mortar tube is indicated by the numeral I8. A recoilless combustion chamber I I is secured to vthe mortar tube I0 by a threaded connection I2 in place of the usual mortar tube cap. The combustion chamber II is provided with an open outwardly flaring nozzle I3 aligned with the bore of the tube I0. A ring-shaped throat member I4 is secured at the inner end of the nozzle I3 seated against a shoulder I5 and is locked in place by one,V or more set screws I6. A, conical memberv IIy issupported centrally within the combustionV chamberrll by means of `a plurality of radial arms I8 of tapered cross-section. The throat member I4, arms I8, and member Il may be formed in one piece. A powder trap plate I9 is secured against; the 'face of member I'I by a trap pin 20, the latter being provided with a shoulder ZI engaging the plate I9 and a threaded stud 22 extending into the central portion of member I1. The trap pin 20 is axially aligned with the mortar tube- ID and may be tapered to facilitate the centering of the propellant charge (not shown) The forward end of pin 20 is shaped to engage and re a percussion igniter carried by the propellant and projectile assembly as it is loaded into the combustion chamber through the tube Ill. 'I'he pin 20 may be provided with an opening 24 therethrough to receive a rod to assist insecuring the Ypin 20 to the member I1. The threaded central portion of member I'I is tted with a` replaceable plug 2'1 having a Venturi opening therein communicating through passages 28 and 24 inthe trap pin 20 with the in-V terior of the combustion chamber I I. A series of plugs 21 having openings of various sizesmay in the combustion chamber IVI.

be approximatelyL-shaped in cross section, andmay be rigidly secured to the nozzle I3 by rivets 26. Although only one vane 25 is shown in- Figs. 1 and 2, it should be understood that-the use of six is intended, so that there will be one vane aligned with each of the V'sixarrn'sy 'IliffY TheYAY vanes, as shown in Fig. 2, are-positionedatan i angle of the order of fteen degrees Withre'spectI to the axis of the tube I and chamber II order to produce a rotation force sufcient to counteract the tendency of the tube 1 I0 andchamber II to rotate as *aV projectile is fired from the rifle'd bore of tube Ill.`

AY 'suitable mountfor the'Tecoillessgun shownV The mode of operation of the embodiment' illustrated'in Figs'.1 and-2 Willnow'be described. Thltube'I' may'be'aimed forhighran'gle fire the same as a conventional 4.2 chemical mor-y tar.l A" regular 'mortar 'projectile carrying a charge `of propellant-powder is inserted within thcombustion chamber II aboutfthe pin 20. As-j th propellantpowder approaches the trap plate 19,- the forward end of pin '20'engages'ignitin'gm'eans carrie'drbythe propellant' and projectile, and actuates'the same by percussion.v The' propellant char-ge burns Withinthe'chamber Il andthe gases produced flow from thech'amber' II `between the arms I8' and' outward through the nozzle |35" Atfthe Sametime, the projectile is propelled forward through" the' Atuber I0, and

the rifling' tube I0 gives the .shell suiicien't"v rotationtostabilize its ighti- The rotational re"-v coil'cau'sed by the Arifling in the'tube IIJ 'is' counter` acted-'and balanced by the now-of gasesaga'inst theangular vane`s12'5fin` the nozzle I3. The angle' ofthevanes25'fwith respect toth'e axisloffthe tube" IUand combustion chamber rII is selected" so that the' mass and velocity` of gasesr'ilowing against the varies producethe 'required rotational force'` to' 'counteract Ythe tendeneyf of the tube' I 0 and `chamber II torota'teV The'momentum im; partedto the projectile'iired' through tube I'is balanced by 'the' momentumof 'the gases escape'VV ingwfthrough the nozzle "I 3 'thereby' providingprecoilless gun" operation. Recoil balance" may be established byusing-a plug 21 havingthe'proper size-opening to cornpensate'for inaccuracies thesiz of throat member I4 due'to'manufactu'ringtolerances or due toL erosion caused through use'of'the gun.

The" propellant chargeffor the recoillessat` taclirnent for'the'4-2 inch chemicall mortarmay comprise a' laminated'V assembly including Vaboutt 270"disk's of 'M'-6"poWder, 0;026"inch thick; 3163y inches in diameter, and 1.125 inchesinside'diam= eter, the vcomplete 'propellant charge-"weighing about 3.5 pounds,A for mortar shellsfw'eighing about;25.'0 pounds.

ignite^thepropellant charge; 1

The modified construction illustrated inlFgs.' Bandi-,4 inCldesf-fa mortar Stube5 3D,"l acornbustion Such a 'chargeIgives' a shell velocity'of the'orderof "120' feet persecond The conventional `mortar percussion means together with an added secondary: igniter maybeusedto 4 chamber 3f and a nozzle '132.7 Alcentr'al ltrap rod 33' 'provided Witha trap' plate V34'fissupported by a central member 35, the latter being carried by a plurality of radial arms 36 and vanes 31.

-Thevanes 31 may be tapered toward the rear of -the nozzle 32 as shown in Fig. 4, one side of each? vane ybeinglat 'an angle of about 3 degrees with-respect -to' the tube and chamber axis and theiother side"of`each vane being at an angle of'about 13 degrees with respect to said axis.

This construction provides an eiective vane angle ofl about 5 degrees which is adequate to produce enough rotational forcee to counteract the tendency ofthe tube 30 to rotate during firing'. The

outer ends of arms 36l and the outer edgesi of vanes' 31 may be welded'to'the'inner surfaceoffl the nozzle 32, and the latter .may 'be'fconnected'f to the combustion chamber '3| by:athreaded"con 1 nection. The central hub member 35'and.trap" rod Sii-'carry' a firingzpin 38 andv afspringtilfforff urging the pin forward forpercussion firing. Av

sliding bar 45 extendingfthrough the externalE l 'portion ofthe firing 'pin' 38 maybe usedito'retain the pin 38 'in the retracted position shown. WhenitheA bar luis pulled clear,I the iiringf'pin" 38'is snapped forward' by the compression' ofw spring 39 until the forward end of pin 38 strikes and rires vsuitable ignition means carried byi'thevr projectile and/or propellant charge.

The'mode of operation of 'the recoilless'mortar'i of the Fig. Sand Fig-4 constructionis-'similar'to. that of the Figs. 1 and 2`constructi'on except thatr the spring operated' i'lring'pin 38 'may be released to rev av propellant'V charge and'shelll loaded through the 'muzzle' finto vthe chamber '3 I at'anyv angle of elevation.

The modified construction illustrated 1in l3ig."5j includes'the rear vportion of`a mortar tube'50, 'a' cylindrical powder 'trap' 5I, and .anfout'er'casingfr 52 connecting the trap 5I to the mortar tuba'eill-v The" 'powderftrapiIv is provided with a pluralityf of axially elongated' slots 53 vpermitting the pas'- 1 sage of' gases resulting from the burning 'of' av propellant within trap 5I fto theann'ular nozzle v or venturi defined by the rear portion' 54 off trap" 5| and the rearY portion 55 of the outer-'casing 52. The trap 5I may be provided withaf shear disc 56 secured'in'place by a Ythreaded ring-51"."y The shear disc 53 serves as-a safety device which will shear or blow out' to the combustion chamber inthe event that excessive pressures'areproduced bythe burning of the vpropellant charge within the trap 5 I. Suitable ignition means (not shown) of the percussion, electrical or electro-magnetic` inductiontype maybe provided for igniting a propellant charge after the 'charge isloaded into the trap 5I through the tube 50.

The construction illustrated in Fig. 6 includes a' combustion chamber 60 Which may be secured tothe rear portion of a mortar tube (not shown) in-'a-manner similar to that shown in Fig. 1. The chamber has a throat or venturi '6| and an. outwardly flaring nozzle 62 aligned with the 'mortar tube. A trap plate 53'is supported in' the combustion chamber 60' by a plurality of radial arms 64 secured to the Walls of the combustion chamber. A trap rod 65 is supported by the plate G3 and the arms 64 in an axial position through the nozzle 62, and the venturi 6I, and extends into the chamber 60. The rod 65 may liavea central bore 66 to contain an electrically oper-1" ated igniter or squibmeans 61. The bore 66' is provided with radial openings 68 within the combustion'chamber, andcon'ductors 69are provided" for connectiontoaiiingcircuit; An4 adjustable" constrictor ball 1U is supported on the rod 65 and is provided with slots 1I to receive a suitable lThe ignition of a propellant charge in the chambfer 68 may be accomplishedV by the electrical igniter means 61 or by percussion means actuated by the forward end of the trap rod 65, as explained heretofore.

Referring to Fig. 7, a modified form of adjustable throat, recoilless combustion chamber is shown, comprising a combustion chamber which is to be secured to the rear portion of a mortar tube (not shown) by threaded interconnection, as shown in Fig. l. The interior of the rear portion 1B of the chamber 1i is Venturishaped and is provided with a plurality (usually six) of vanes 11, which also serve as supporting spokes for a hub 18. The exterior of the hub 18 Yis shaped so as to complement the shape of the end section 16 and thus form a Venturi throat 19 at the outlet of the chamber 15.

An integral firing pin 80 and powder trap 8| is supported in the front of the hub 18 as shown,

, while a hallowed-out plug 82 is supported in the rear of the hub 18. The hollowed-out portion of the plug 82 is Venturi-shaped, as shown, and permits the outlet of gases escaping through the port holes 83 in the powder trap 8 I.

Due to manufacturing tolerances, it is not practical to obtain perfect balance of recoil without the use of some adjusting means for varying the effective area of the nozzle opening. By providing a series of plugs, such as plug 21 in Figure 1 or plug 82 in Figure 7, having Venturi openings of various sizes and insertable in the central member of the nozzle in communication with the combustion chamber, a plug of the proper size may be quickly inserted to establish recoil balance. Consequently after repeated rings result in erosion which upsets the recoil balance, the balance may be re-established by substituting a plug having a smaller opening therein.

Where the recoilless combustion chambers described above are to be used for high angle iiring of projectiles loaded through the muzzle of the gun tube or barrel, percussion type igniters may be used. In such cases, the propellant charge and projectile move down the gun tube or barrel by gravity until the propellent charge is within the combustion chamber and a flxed firing pin in the chamber engages and res an igniter by percussion. In low angle '.re at point blank ranges gravity may be insufficient to move a projectile and the propellant charge from the gun muzzle into ring engagement with a fixed firing pin. In these cases the projectile and propellant charge may be pushed into the ring position by a rain and then be red by the spring ring pin of the Fig. 3 construction, or the propellant charge may be red electrically by a squib connected to an external electrical circuit by conductors extending outward through the nozzle or venturi of the combustion chamber (as shown in Fig. 6), or it may be fired electrically by voltages induced in an enclosed ignition circuit by electromagnetic induction. (It is also feasible to provide percussion type ignition by the use of driver means to propel the projectile and propellant charge from the gun muzzle to the ring position at all angles of fire. A driver rocket for use in this connection is disclosed in my copending application, Serial No. 594,241, iiled May 17, 1945, now Patent 2,519,905.)

It will be apparent that the recoilless gun constructions shown and described herein provides a relatively light Weight gun having a few readily portable parts. The recoilless gun may be easily set up for use on a light mount, or on a movable mount such as a light vehicle or an airplane. The recoil forces are balanced, including both axial and rotary recoil forces. The application of the principles of my invention to a muzzle loaded gun, such as the 4.2 inch chemical warfare service mortar does not limit the rapid re characteristics of such weapons.

Numerous variations and modications of my invention will be apparent from the several constructions described herein, and the invention is to be limited only by the Scope and spirit set forth in the following claims.

I claim:

1. In a recoilless gun having a casing provided with a pressure developing chamber and a coaxial exhaust passage leading therefrom to the rear exterior thereof, a spider-like member removably xed within said chamber. said member having a hub portion coaxial with said chamber and a plurality of integral vanes angularly disposed relative to the axis of and extending from said hub portion toward the walls of said chamber whereby to deflect and give a circular motion to gases exhausted axially through said exhaust passage said hub portion having a central internally threaded bore extending therethrough, a centrally recessed replaceable trap plate removably mounted on the front surface of said portion, and an elongated externally threaded replaceable trap pin threadedly secured in said bore in alignment with the bore of said gun.

2. The gun of claim 1 in which the trap pin is provided with a gas conduit leading from the front of said trap plate to the rear end of said pin and in which there is also provided a recessed plug threadedly secured in the bore of said portion to the rear of said trap pin, and adapted to restrict the backward ow of gaseous products of explosions through said hub portion.

CLARENCE N. HICKMAN.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,280,579 Stone et al. Oct. 1, 1918 1,380,358 Cooke June 7, 1921 1,661,091 Riabouchinski Feb. 28, 1928 2,344,957 Anzalone Mar. 28, 1944 2,405,414 Eksergian Aug. 6, 1946 2,421,522 Pope June 3, 1947 FOREIGN PATENTS Number Country Date Y 570,257 France Jan. 15, 1924 468,583 Great Britain July 8, 1937 373,378 Italy July 25, 1939 

